Accepted Manuscript Molecular mechanism of anionic dyes adsorption on cationized

ACCEPTED MANUSCRIPT
6 
analytical grade without any pretreatment and purchased from Kemiou Chemical 
Reagent Co., Ltd (Tianjin, China), such as NaClO
2
, NaHSO
3
, NaOH, Epichlorohydrin 
and other chemicals.
2.2 Preparation of cationic rice straw cellulose 
Rice husks (RH) used in the experiment was supplied by a local rice factory. 
Waste rice husks was cleaned in order to remove impurities, and dried in sunlight. The 
dried waste rice husks was crushed by a grinder and passed through a 30-mesh sieve. 
In order to remove hemicellulose and lignin, the milled rice husks was soaked into a 
mixed solution composed of 40 g L
-1
of NaOH and 2 g L
-1
of NaHSO
3
solution with a 
bath ratio of 50 g: 1 L, and stirred at 90°C for 3 h, then washed with a large amount of 
distilled water, dried in a vacuum oven at 60°C. The reaction was carried out to 
remove lignin with other impurities such as hemicelluloses, pectin, and waxy 
materials. After the alkali treatment, the delignified rice husks (RHD) was placed into 
a mixed solution composed of 10 g L
-1
of NaClO
2
and 5 g L
-1
of acetic acid at a bath 
ratio of 35 g: 1 L, and stirred at 70°C for 1 h, with the purpose of removing the 
remaining lignin and hemicelluloses. The upper treatment process was repeated three 
times to obtain the pure rice husks cellulose, which was dried in a vacuum oven at 
60°C. The bleaching treatment breaks down the phenolic compounds and 
chromophoric groups present in the lignin molecule, thus whitening the RHD sample. 
Finally, the dried cellulose was ground to a powder with a size of 40 mesh for further 
modification process (RHC). 
To prepare cationized rice husks cellulose (CRHC), 10 g of rice husks cellulose 
was added to 250 mL of 20% NaOH solution, treated with an ultrasonic cell (10.8 kJ 
g
-1
, 5 min) and stirred at room temperature for 2 h. The suspension was filtered and 
the solids were added to 250 mL of 10% NaOH solution and 240 ml of 
epichlorohydrin, heated to 65 °C in a water bath, and stirred for 6 h. After the reaction, 
the suspension was filtered and washed with isopropyl alcohol to remove the 
unreacted epichlorohydrin. The obtained solid was added to a 200 mL mixture 
solution with 40 vl% N, N-dimethyl-1-octadecylamine/isopropanol, heated to 80°C 

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